Well-established power distribution systems exist throughout most of the United States, and other countries, which provide power to customers via power lines. With some modification, the infrastructure of the existing power distribution systems can be used to provide data communication in addition to power delivery, thereby forming a power line communication system (PLCS). In other words, existing power lines that already have been run to many homes and offices, can be used to carry data signals to and from the homes and offices. It will be understood that for purposes of this specification, the term “data signals” will encompass any information carrying signal such as packetized data using protocols such as the transmission control protocol (TCP) and internet protocol (IP) as well as non-packetized framed data such as video or voice. These data signals are communicated on and off the power lines at various points in the power line communication system, such as, for example, near homes, offices, Internet service providers, and the like.
While the concept may sound simple, there are many challenges to overcome in order to use power lines for data communication. Power lines are not designed to provide high speed data communications and are very susceptible to interference. Additionally, federal regulations limit the amount of radiated energy of a power line communication system, which therefore limits the strength of the data signal that can be injected onto power lines. Consequently, due to the attenuation of the power lines, data signals typically will travel only a relatively short distance on power lines even though power transmission distances may vary from location to location.
An exemplary portion of a power line communication system is shown in FIG. 2 and includes one or more bypass devices (BD) 80 to communicate data signals around the distribution transformer that would otherwise filter such data signals. In this example, BD 80 serves as a gateway between the LV power lines and the MV power line and communicates signals to and from the user devices at the customer premises (CP), preventing them from passing through the transformer or significantly degrading them. Thus, BD 80 is the gateway between the LV power line subnet (i.e., the devices that are communicatively coupled to the LV power lines) and the MV power line and communicates signals to and from user devices at the customer premises (CP) via the low voltage subnet 61.
The BD 80 provides communication services for the user, which may include security management, routing of IP packets, filtering data, access control, service level monitoring, signal processing and modulation/demodulation of signals transmitted over the power lines.
The exemplary PLCS also includes a backhaul point 10. The backhaul point 10 is an interface and gateway between a portion of a PLCS (e.g., an MV run) and a traditional non-power line telecommunications network. One or more backhaul points (BP) 10 are communicatively coupled to an aggregation point (AP) 20 that in many embodiments may be at (e.g., co-located with), or connected to, the point of presence to the Internet. The BP 10 may be connected to the AP 20 using any available mechanism, including fiber optic conductors, T-carrier, Synchronous Optical Network (SONET), or wireless techniques well known to those skilled in the art. Thus, the BP 10 may include a transceiver suited for communicating through the communication medium.
As discussed above, due to the design of power lines, data signals which are typically high frequency signals superimposed on the low frequency power signals, are attenuated very quickly. Thus, the PLCS network design often must install numerous backhaul points, which further requires installing backhaul media to connect the backhaul point to the upstream device. However, this can be inefficient and expensive.
A proposed solution has been to insert data signal repeaters along MV power lines to periodically regenerate data signals. However, as will be more fully discussed below, repeaters may introduce unwanted latency to data signals. Such latency, while tolerable for some data communications (e.g., latency insensitive data such as web page data), is undesirable for more time sensitive data such as voice or video.
Finally, there may be concern that any device that interfaces with the MV power line be designed to minimize any potential interruption of power service for a large number of customer premises. One must be mindful that the primary purpose of a power line system is the delivery of power and the potential for interruption of power delivery must be minimized by reducing the need for physically cutting into the MV power line to install a device.
Thus, there is a need for a device and method that enables amplification of data signals along the power line so that the number of backhaul points required for effective data signal transmission may be reduced. In addition, there is a need for a device that provides amplification to power line communication signals that can be installed without cutting the power line and that provides low latency amplification.
These and other advantages may be provided by various embodiments of the present invention.